[Package.swift] Require swift-llbuild and swift-tools-support-core using semver dependencies

Author: abertelrud

Package.swift

@@ -210,7 +210,7 @@ import class Foundation.ProcessInfo
 if ProcessInfo.processInfo.environment["SWIFTPM_LLBUILD_FWK"] == nil {
     if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
         package.dependencies += [
-            .package(url: "https://github.com/apple/swift-llbuild.git", .branch("swift-5.2-branch")),
+            .package(url: "https://github.com/apple/swift-llbuild.git", .exact("0.3.0")),
         ]
     } else {
         // In Swift CI, use a local path to llbuild to interoperate with tools
@@ -224,7 +224,7 @@ if ProcessInfo.processInfo.environment["SWIFTPM_LLBUILD_FWK"] == nil {
 
 if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
     package.dependencies += [
-        .package(url: "https://github.com/apple/swift-tools-support-core.git", .branch("swift-5.2-branch")),
+        .package(url: "https://github.com/apple/swift-tools-support-core.git", .exact("0.1.0")),
     ]
 } else {
     package.dependencies += [